The invention is based on a fuel injection nozzle for an internal combustion engine. In a fuel injection nozzle of this kind, which in this instance opens inward, it is known to cause a valve needle tang to move in the opening direction until it stops at a spring-loaded supplementary mass, so that a shock-absorbing braking effect is attained during the opening movement. The supplementary mass displaces fuel from a damping chamber via a calibrated flowthrough opening, and the fuel flows back into the damping chamber through the same calibrated opening in the interval between opening strokes of the valve needle. (British Patent No. 720,011). The supplementary mass which damps the valve needle movement is disposed in an axial elongation of the valve needle, so that the resultant injection nozzle is quite long; it is also disadvantageous that the generally smaller masses and available damping chambers do not permit a precise adaptation and adjustment of the manner in which the valve needle movement takes its course. Intervening in order to prevent disadvantageous recoiling in the case of such valve needles with a high closing speed is not possible.
In a further known fuel injection nozzle for internal combustion engines (German Auslegeschrift No. 20 52 311) the valve needle does cooperate with a spring-loaded annular piston, but not for the purpose of damping needle movement; instead, the intention is to form a reservoir of variable volume, so that a substantial increase in fuel pressure at the moment of injection is avoided. The annular piston acts as a buffer, counter to the force of its helical spring, and it is initially deflected so as to increase the pressure chamber volume of the supplied fluid quantity.
In order to attain adaptation and optimizing both in injection valves opening in the flow direction (so-called A-valves) and in valves opening counter to the flow direction, it is desirable to influence the opening and closing movements in a precisely intended manner, because these movements, in cooperation with the coupled outflow cross section of the injection ports, shape the course of injection. There is a general trend toward miniaturization, which exists even in conventional, inwardly opening injection nozzles (I-nozzles); in addition, however, particularly small nozzle needle injection tangs (in A-valves) are required for providing the stream-type fuel preparation also demanded at the present time. This, in turn, results in valve neeldes of very small diameter, compared with conventional nozzles. Such small valve needles, however, enable an adaptation of the inherent frequency and the optimal damping only in narrow operating ranges; as a result, an adaptation of these injection nozzles over the complete performance graph of the engine cannot be attained. For instance, phase displacements may occur as a consequence of oscillations of the valve needle between the discharge cross section of the valve and the pressure inside the valve, which at times of low pressures in the valve chamber cause combustion gases to flow out of the engine combustion chamber into the interior of the valve, possibly depositing soot at the functionally important metering cross section and eventually charring it. The course of injection in particular, and accordingly the course of combustion, are unfavorably influenced by these oscillations. The result is rough engine operation, which produces unfavorable toxic and particulate emissions. Valve charring causes the angle of the fuel stream to widen, and there is increased combustion noise, which results in an impairment in terms of mixture formation, fuel consumption and smoke emissions.
There is accordingly a need for a fuel injection nozzle which is small in struture and those opening and closing movements can be variably and intentionally influenced.